With the development of technologies, current mobile communication terminals (such as cell phones, tablet computers, and so on) have had very broad applications.
Because all mobile communication terminals are powered by batteries, their continuous service time is limited. When the battery is used up, it has to be charged. However, frequent charging operations disturb the user's normal usage. More seriously, if the user forgets to charge the device, the problem that the device is not usable may be caused.
In particular, with the popularization of smart phones, the above problems become more notable. Smart phones have larger power consumption though they have more functions, but the energy storage capacity of batteries cannot be increased unlimitedly such that the smart phones have shorter continuous service time. Usually, many smart phones need to be charged every one or two days, which degrades users' usage experience dramatically.